Purify the salt by dissolving it in the minimum volume of hot water (60o) and adding EtOH, with stirring, then leave at 0o for 1hour. The crystals are filtered off and recrystallised from H2O until free of Cl and SO2-ions. Dry it in a vacuum over P2O5 at room temperature. It is a specific substrate for arylsulfatases which hydrolyse it to p-acetylphenol [max 327nm ( 21700 M-1cm-1)] [Milsom et al. Biochem J 128 331 1972].
